One TENS device is described in the Rossen U.S. Pat. No. 4,989,605. It is believed this device has been sold on the market by the trade name “MicroStim”. The Rossen '605 patent discloses a microcurrent TENS unit that uses a unique wave form. It is proposed the current is from 250 microamps up to about 900 microamps with a peak current of six milliamps. The current is applied through a pair of electrodes in the form of high-frequency monophasic bursts of a direct current with a carrier signal from around 10,000 Hz to 19,000 Hz. The signal is modulated at a relatively lower frequency (0.3 Hz up to 10,000 Hz). These modulated carrier signals are from about 0.05 seconds to 10 seconds in duration with above one second being the preferred duration. The electrodes are reversed as simulating a biphasic form yet the character is a monophasic DC signal. The Rossen patent is for palliative pain treatment only.
The Wallace U.S. Pat. No. 5,522,864 proposes that macular degeneration or other ocular pathology may be treated by placing a positive electrode of a direct microcurrent source in contact with the closed eyelid of the subject and placing a negative electrode away from the eye of the subject, preferably on the neck of the subject. These electrodes apply a constant direct current of 200 microamps for approximately 10 minutes. It is proposed that this device can be portable and battery powered, hence allowing a subject undergoing the treatment to ambulate during the treatment. The Wallace patent proposes using microcurrent to treat macular degeneration but does not disclose the mechanism by which positive results are obtained.
The Jarding et al. U.S. Pat. No. 6,275,735 proposes digital control of the modulation frequency of the microcurrent signal. The modulation frequency is controlled by a digital data word. A controller is coupled to a digital analog converter and supplies the digital analog converter with digital data words to generate an electrical signal for the microcurrent stimulation therapy. It is believed that this form of microcurrent therapy may be particularly useful in macular degeneration. More specifically, the Jarding patent proposes that adenosine triphosphate levels in cells can be affected by appropriate electrical stimulation. Jarding proposes that electrical stimulation to the cells increases blood vessel permeability, increasing ATP levels and increasing protein synthesis. Therefore, Jarding concludes that microcurrent stimulation can help rejuvenate cells in the retina to slow or stop degeneration of the eye due to age-related macular degeneration. Therefore, Jarding proposes a computer controlled electrical stimulation to maximize therapeutic benefits by varying the types of wave forms and frequency ranges used in the therapy.
Another problem present in the use of TENS units for therapeutic or palliative effect is patient compliance. Wingrove U.S. Pat. No. 5,800,458 proposes a compliance monitor to determine if the patient is using the TENS unit in accordance with instructions or prescriptions. Another problem with conventional TENS units is they can be bulky or difficult to control. This can especially apply to individuals who have some disability or who are in acute pain. Michelson et al. U.S. Pat. No. 6,445,955 proposes a miniature wireless TENS unit. A remote controller sends transmission signals to a receiver within an electronic module with the TENS unit allowing the patient to program specific units in a specific way. The TENS unit itself may be incorporated within a bandage or electrode package and worn directly on the patient's body.
It has also been proposed, at least in a research context, that the wrong current levels used in transcutaneous electrical nerve stimulation can actually reduce ATP levels and may cause more harm than good. Research by Ngok Chen would demonstrate, at least in rats, that current levels in the microamp range tended to increase ATP concentration in cells while currents in the milliamp range tended to lower ATP concentration in cells. (See Chen, The Effects of Electrical Current on ATP Generation, Protein Synthesis, and Membrane Transport in Rat Skin, Clinical Orthopedics Research, 171, November–December 1982, pp. 264–271) It has also been suggested by Thomas W. Wing, D.C., N.D. that direct current employing a carrier wave with a low frequency is very helpful triggering the repair process in muscles. Wing suggested only very low levels of stimulation are required if the effect of the direct electrical current at a low frequency was the triggering of the body's natural repair cycle. Wing suggests that low frequencies of 0.1 to 0.3 Hz produce lasting therapeutic effects, but pain relief is more rapid at higher frequencies in the 10 to 100 Hz range. Thomas W. Wing, D. C., N. D. Chiropractic Economics, March/April 1987. The Food and Drug Administration has approved the use of TENS units for symptomatic relief of chronic pain and to manage post surgical traumatic pain problems. The therapeutic use to treat macular degeneration proposed by Wallace et al in the '864 patent is an off label use of a TENS device, that is, this use is not approved by the FDA. However, in order to obtain FDA approval for a TENS unit for treatment of degenerative diseases such as macular eye disease, tissue repair, and cell regeneration, require proof of effectiveness. Proof is obtained through double blind, randomized, and multi-site clinical trials. It is believed such trials are underway to document effectiveness of a TENS unit for the treatment of age related macular degeneration.
The use of a TENS unit both for palliative and therapeutic treatment is well established, but the precise mechanism by which it operates is not fully understood. This means that even small differences in how an electrical current is applied can have unpredictably large changes in the therapeutic outcome. That is to say, a current of 200 microamps might be therapeutic, while a current of 400 microamps might actually be harmful. By the same token, such factors as whether the current is applied in a wave form, whether the polarity of the current alternates, and the like all can have important impacts in either the palliative or the therapeutic effect. Consequently, the optimal use of a TENS unit for either palliative or therapeutic effects proceeds more by experimentation than by theoretical design. That is to say, there is no theory by which one can design an ideal or maximally beneficial treatment modality for a particular TENS unit, then experiment to confirm the correctness of the program. Theory may point one in the right direction, but then an inventor must use intuition, clinical judgement, and experimentation to arrive at a therapeutic program giving maximum benefits.
Despite this earlier work there is still need for a TENS unit and treatment method to meet specific goals and needs. First, in the correct method, the TENS units must always operate in a current range that maximizes the benefits of the electrical nerve stimulation. Second, the duration and frequency of the electrical stimulation must be controlled to maximize the benefits. Third, control of the TENS unit should be designed to maximize compliance of a patient. Therefore, it is an object of the current invention to provide a fully automated and computer controlled microcurrent stimulation device. It is a further object of the invention to administer a therapeutic electrical current in the microamp range, always less than one milliamp. It is a further object of the invention that the current be administered in a square wave form in a sequential pattern of specific electrical bursts with frequencies between 0.1 Hz and 300 Hz. It is a further object of the invention to control the duration of the application of each electrical current bursts with the specified frequency for a specific period of time and sequence the application of the current controlled by an internal control to minimize patient compliance issues and to maximize benefit. It is a further object of this invention to periodically reverse the polarity of the current flow at specific intervals. It is a further object of this invention to give visual and audible cues as to the treatment being administered at any given time. It is an object of the invention to provide minimal controls or requirements for patient input or control. It is a further object of the invention that the TENS unit will be ergonomically designed and easily used by those with physical disabilities.